Method of developing a high contrast, positive photoresist using a developer containing alkanolamine

ABSTRACT

Compositions and methods for developing quinone diazide positive-working photoresists. The compositions consist essentially of an aqueous solution of a tetraalkylammonium hydroxide primary alkali and an alkanolamine having the following structure: ##STR1## wherein n is zero or 1, and each R is independently selected from hydrogen, methyl, or ethyl. The methods involve use of this composition to develop the indicated photoresists. The addition of an alkanolamine of the indicated type prevents the formation of irregular deposits on the edges of unexposed portions of the photoresist lines when the photoresist is developed. Selection of these alkanolamines also increases the uniformity of line widths of photoresist lines developed according to the present invention, and increases the process latitude of the developer.

TECHNICAL FIELD

This invention relates to processes for developing quinone diazidepositive-working photoresists, particularly high contrast resists usedin the fabrication of integrated circuits on single-crystal wafers.

BACKGROUND ART

Quinone diazide positive-working photoresists, and similarpositive-working compounds used in the preparation of lithographicprinting plates, are described in U.S. Pat. No. 4,464,461, issued toGuild on Aug. 7, 1984, particularly from column 3, line 39 to column 7,line 16. The foregoing patent is hereby incorporated herein byreference. Commercial photoresists of this kind include OFPR-800; otherphotoresists sold by the Dynachem division of Morton Thiokol, Inc.,Tustin, Calif.; and products sold by Shipley Company, Inc., Newton,Mass.; Eastman Kodak Company, Rochester, N.Y.; and others.

A positive-working photoresist functions by being coated on a suitablesubstrate, image-wise exposed to actinic radiation, then subjected to adevelopment process which removes those portions of the photoresistwhich were previously exposed to radiation, leaving the unexposedportions of the resist intact. The developed photoresist patternprotects the corresponding portions of the substrate from a furtheroperation performed on the substrate, such as ion implantation, etching,plating, or the like. (In the case of printing plates, the residualportions of the photoresist have a different affinity for ink than theexposed portions of the substrate.) The known developers for quinonediazide positive-working photoresists comprise an aqueous solution of analkali. The concentration of alkali is chosen to provide a developerwhich will selectively attack the exposed portion of the photoresistunder the exposure and development conditions which have been selected.

While some commercially available developers contain metal salts such assodium carbonate, sodium hydroxide, and others as alkaline agents, theart has recently chosen to avoid metal ion containing alkalinematerials, or other metal ion sources, in photoresist developers. Aconcern has developed that residual metal ions left by the developermight form conductive paths in the finished device. Because of thisavoidance of metal ion containing developers, the preferred alkalinematerials are now tetraalkylammonium hydroxides, and particularlytetramethylammonium hydroxide (TMAH). TMAH based developers arediscussed in U.S. Pat. No. 4,423,138, issued to Guild on December 27,1983; U.S. Pat. No. 4,464,461, issued to Guild on Aug. 7, 1984; EuropeanPatent Application No. 0,062,733, filed by Cawston et al on Jan. 28,1982 and published on Oct. 20, 1982, based on a corresponding U.S.patent application filed Apr. 10, 1981; Grieco et al, "PhotoresistDeveloper Compounds", IBM Technical Disclosure Bulletin, Volume 13,Number 7 (December, 1970); "Improved Resist Developer," ResearchDisclosure 22713, March, 1983, pages 98-99; and others.

Several prior patents show the possibility of using an alkanolamine,particularly ethanolamine, in photoresist developers. According to itsEnglish language abstract, Japanese patent application No. 59-119105,believed to have been published December 26, 1985, teaches the use ofeither an inorganic alkali or an organic amine such as monoethanolamineor ethylenediamine as an alkaline agent in a photoresist developer. U.S.Pat. No. 4,464,461, column 1, lines 40-43 indicates that developerscontaining, for example, alkanolamines are "well known". U.S. Pat. No.4,530,895, issued to Simon et al on July 23, 1985, at column 1, lines59-62, suggests use of a developer containing an alkaline substance suchas diethylamine, ethanolamine, or triethanolamine as a photoresistdeveloper. U.S. Pat. No. 4,411,981, issued to Minezaki on Oct. 25, 1983,discloses from column 3, line 46 to column 4, line 8, the use of adeveloping and etching solution for a photoresist containing variousorganic bases such as TMAH, monoethanolamine, diethanolamine, andtriethanolamine, among many other basic reacting compounds. None ofthese references suggests any reason to mix a quaternary ammoniumcompound and an alkanolamine to correct any shortcoming of eithermaterial used alone as a developer.

As will be shown in comparative examples, TMAH used alone as aphotoresist developer causes what appears to be a deposit of flakyresidue along the upper and lower edges of lines of developedphotoresists, particularly high contrast photoresists. The presence ofthis residue in exposed areas (which are intended to be free ofphotoresist) suggests potential problems.

Alkanolamines by themselves are not suitable as developers for highcontrast photoresists of the type exemplified herein, as they developlines with poor resolution, fail to develop them altogether, or stripthe photoresist. High concentrations of these developers also roughenthe upper, normally smooth surfaces of developed photoresist lines.

One continuing challenge, as circuit geometries shrink and qualitystandards are maintained or raised, is how to maximize line widthuniformity. Good line width uniformity means that lines of developedphotoresist have nearly the same nominal line width and other dimensionsas the mask lines and that these dimensions don't vary significantlydepending on the location of the line on the wafer, the location of thewafer in a boat in which a batch of wafers are immersion processedtogether, or the order in which wafers are spray processed.

Another continuing challenge in photoresist developer research is how toachieve the desired line width uniformity despite variations indevelopment conditions from the nominal conditions selected fordevelopment. A developer composition having this property is said tohave wide process latitude.

It is further desirable that a photoresist developer not cause the sidewalls of the developed photoresist to become less vertical.

SUMMARY OF THE INVENTION

One object of this invention is to solve the residue problem of TMAH orsimilar photoresist developers while retaining or improving line widthuniformity and process latitude of such developers. A further object isto accomplish the preceding object with a developer which is usable incommercial automated equipment, especially spray equipment which demandsthat a developer be easily sprayable.

One aspect of the invention is a method for developing an exposedquinone diazide positive-working photoresist without forming irregulardeposits on the edges of unexposed portions of the photoresist. Themethod comprises the steps of providing an exposed photoresist fordevelopment; providing the developer previously defined above;developing the photoresist with the indicated developer until thepattern is cleared; and rinsing the developer from the photoresist.

The developer consists essentially of an aqueous solution of an alkaliand an alkanolamine. The alkali is a tetraalkylammonium hydroxide, andis present in the composition in an amount sufficient to enable thecomposition to develop the photoresist. The alkanolamine has thefollowing structure: ##STR2## In the above structure, n is 0 or 1, andeach R is independently selected from hydrogen methyl, or ethyl.

The amounts of the alkali and the alkanolamine to be used can bevariously expressed to accomplish different objectives. First, thealkanolamine component is present in the composition in an amountsufficient to reduce formation of the previously mentioned irregulardeposits on the edges of unexposed portions of the photoresist duringdevelopment of the photoresist. Second, the alkanolamine can be presentin an amount sufficient to increase the C_(p) value of the composition,as defined later in this specification. Third, the alkanolamine can bepresent in an amount sufficient to increase the process latitude of thecomposition, as defined later in this specification.

In a preferred aspect of the invention, about 0.7 to about 1.6% byweight of the tetraalkylammonium hydroxide is present, and the ratio ofthe hydroxide to the alkanolamine is less than or equal to about 1:9 byweight. The composition can optionally contain from about 0 to 0.05% byweight of a surfactant to improve the sprayability of the compositionand to avoid the problem of dewetting the resist during development.

A second aspect of the invention is a similar method in which enough ofthe previously stated alkanolamine is present in a developer to providea C_(p) value of at least about 1.33 for the developer as used todevelop a quinone diazide positive-working photoresist.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1 through 6 are each a perspective fragmentary photographic viewof a developed two micron (nominal mask dimension) photoresist line,also illustrating the surrounding substrate and a portion of theadjacent line. Each photograph was taken at a magnification of 20,000diameters, at an energy of 23 KV, using a scanning electron microscope.FIGS. 1 through 6 show lines developed according to Examples 35 through40, respectively. FIG. 6 represents the state of the art prior to thepresent invention, and FIG. 5 shows development using an alkanolaminenot within the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Photoresist developers according to the present invention consistessentially of a solvent, a primary alkali, an alkanolamine as definedherein, and optionally a surfactant and various other minor ingredients.

While various organic solvents are used in some photoresist developers,for the present purpose the preferred solvent is deionized water. Theamount of water used is dictated by the amounts of other ingredients.While the amount of water is not generally critical, the compositionsdescribed herein contain from about 60% to about 94% by weight water.

The primary alkali, referred to elsewhere herein simply as the alkali,is the primary ingredient which dissolves exposed portions of thephotoresist when the photoresist is developed. Varioustetraalkylammonium hydroxides have been used or suggested as suitableprimary alkaline compounds; the use of any of these well known compoundsis contemplated in the broadest aspect of the present invention.Although various of these compounds have been selected for differentpurposes, the most common selection is tetramethylammonium hydroxide(TMAH). The art has largely adopted TMAH to the exclusion of othertetraalkylammonium hydroxides as the primary alkali of choice.

It should be noted that the alkanolamines described below are alsoalkaline in water solution, and the prior art has suggested their use asalkaline materials in photoresist developers. Consequently, inclusion ofsubstantial amounts of these materials will contribute to the alkalinityof the developer, and thus reduce the amount of primary alkali which isnecessary.

The amount of alkali useful herein is most broadly more than 0.5% byweight, preferably from about 0.7 to about 2% by weight, more preferablyfrom about 0.8 to about 1.6% by weight, and most preferably from about0.9 to about 1.1% by weight. The amount of primary alkali used in aparticular formulation must be adjusted to account for the influence ofthe other ingredients thereof.

The alkanolamines useful herein are those specified previously in theSummary. Table I which follows recites all the alkanolamines within thepreviously stated generic formula:

                  TABLE I                                                         ______________________________________                                        Alkanolamine Species                                                          Species #    Name                                                             ______________________________________                                         1           1-amino-2-hydroxyethane                                           2           1-amino-2-hydroxypropane                                          3           1-amino-2-hydroxybutane                                           4           1-hydroxy-2-aminopropane                                          5           2-amino-3-hydroxybutane                                           6           2-amino-3-hydroxypentane                                          7           1-hydroxy-2-aminobutane                                           8           2-hydroxy-3-aminopentane                                          9           3-amino-4-hydroxyhexane                                          10           1-amino-3-hydroxypropane                                         11           1-amino-3-hydroxybutane                                          12           1-amino-3-hydroxypentane                                         13           1-amino-2-methyl-3-hydroxypropane                                14           1-amino-2-methyl-3-hydroxybutane                                 15           1-amino-2-methyl-3-hydroxypentane                                16           1-amino-2-ethyl-3-hydroxypropane                                 17           2-hydroxy-3-aminomethylpentane                                   18           3-aminomethyl-4-hydroxyhexane                                    19           1-hydroxy-3-aminobutane                                          20           2-amino-4-hydroxypentane                                         21           2-amino-4-hydroxyhexane                                          22           2-amino-3-hydroxymethylbutane                                    23           2-amino-3-methyl-4-hydroxypentane                                24           2-amino-3-methyl-4-hydroxyhexane                                 25           2-amino-3-hydroxymethylpentane                                   26           2-amino-3-(1-hydroxyethyl)-pentane                               27           3-hydroxy-4-(1-aminoethyl)-hexane                                28           1-hydroxy-3-aminopentane                                         29           2-hydroxy-4-aminohexane                                          30           3-amino-5-hydroxyheptane                                         31           2-hydroxymethyl-3-aminopentane                                   32           2-hydroxy-3-methyl-4-aminohexane                                 33           3-amino-4-methyl-5-hydroxyheptane                                34           3-amino-4-hydroxymethylhexane                                    35           2-hydroxy-3-ethyl-4-aminohexane                                  36           3-amino-4-ethyl-5-hydroxyheptane                                 ______________________________________                                    

As the comparative examples provided below will illustrate, severalcompounds structurally related to the alkanolamines specified aboveeither interfere with the development process or do not provide thebenefits of the present invention. Thus, diols such as propylene glycol;diamines such as ethylenediamine; and di- or trialkanolamines have beenfound not to be useful herein.

The preferred alkanolamines are species 1, 2, and 10 as stated in TableI. These alkanolamines are all suitable for photoresist development byimmersion. Most preferred is species 10, which has also been found to besuitable for spray development of photoresists.

The proportion of alkanolamine contemplated herein is determined largelyby the ratio of the primary alkali to the alkanolamine by weight. Thisratio is no more than 1:9, preferably 1:12 to 1:38, and most preferablyabout 1:15 if the alkanolamine is 1-hydroxy-3-aminopropane. The lowerlimit is provided in the preferred range of ratios because when theindicated maximum proportion of alkanolamine is exceeded, the surfacesof developed lines will be roughened. The upper limit of the range ofratios is specified to provide a noticeable reduction in the amount ofresidue formed. The most preferred ratio has been found to minimize theresidue problem at minimal cost while avoiding the roughening effect ofexcess alkanolamine. These ratios will be found to vary with theproportion and selection of primary alkali and with the choice of aparticular alkanolamine.

The desired amount of alkanolamine will typically be from about 10% toabout 40% by weight of the composition. A preferred range is from about14% to about 21% by weight.

The present compositions may optionally contain a surfactant, inparticular a nonionic surfactant, to improve the sprayability andwetting properties of the formulation. In some spray developmentequipment, some of the present compositions will emerge from the spraynozzle as a cohesive stream of fluid, rather than as finely atomizeddroplets. The result can be that the developer is not adequatelydistributed during the spray step. The addition of certainalkanolamines, particularly in large amounts, has been found to reducethe sprayability of the compositions. This effect is believed to resultfrom changes in the viscosity or the surface tension of thecompositions.

Another fault which some of the indicated developers have is a tendencyto dewet, or withdraw from, the photoresist pattern during development.This reduces the amount of time the photoresist pattern is exposed tothe developer, and thus inhibits development. The presence of a nonionicsurfactant alleviates this problem too.

The preferred nonionic surfactants are the polyethylene oxidecondensates of alkyl phenols. These compounds include the condensationproducts of alkyl phenols having an alkyl group containing from about 6to 12 carbon atoms, in either a straight chain or branched chainconfiguration, with ethylene oxide in amounts equal to 5 to 25 moles ofethylene oxide per mole of alkyl phenol. The alkyl substituent in suchcompounds can be derived, for example, from polymerized propylene,diisobutylene, octene, or nonene. Examples of compounds of this typeinclude nonylphenol condensed with about 9.5 moles of ethylene oxide permole of nonylphenol, dodecyl phenol condensed with about 12 moles ofethylene oxide per mole of phenol, dinonyl phenol condensed with about15 moles of ethylene oxide per mole of phenol, and diisooctylphenolcondensed with about 15 moles of ethylene oxide per mole of phenol. Oneparticular surfactant which has proven useful herein is TRITON X-100,marketed by Rohm and Haas Co., Philadelphia, Pa. The useful amount ofsurfactant is limited by the tendency of such surfactants to degrade theoptimal vertical wall structure of the developed lines of photoresist.The preferred composition, therefore, contains no more than about 0.05%by weight of a nonionic surfactant. Some compositions require nosurfactant at all.

Other components, such as preservatives for TMAH, dyes, wetting agents,cosolvents, buffers, and the like may be added to developers accordingto the present invention. The preferred additives are essentially freeof metal cations.

For purposes of the present specification, an amount of the primaryalkali effective to develop the photoresist is determined experimentallyby providing a proposed composition and varying the amount of alkali tofind a concentration which will develop the photoresist withoutstripping it. The necessary amount of the primary alkali will bedetermined by many factors, including the presence of an alkanolamineand any other alkaline constituents of the developer; exposure energy;line geometries; development mode and conditions; and temperature. Theexamples in this specification provide specific compositions which havebeen found to perform well. One of ordinary skill in the art can readilyformulate a developer having an appropriate amount of the primary alkalito develop the selected photoresist.

Similarly, the amount of the alkanolamine which is sufficient to reduceformation of irregular deposits on the edges of unexposed portions ofthe photoresist during development will depend on the developerformulation, process conditions, the photoresist used and how it isapplied, and other factors. An amount of alkanolamine sufficient toreduce formation of irregular deposits is determined qualitatively byexamining scanning electron microscope photomicrographs of photoresistsdeveloped with various developers to select the optimal developer for agiven task. When the amount of the alkanolamine is expressed as anamount sufficient to increase the C_(p) value of the composition, C_(p)values of the composition under the desired development conditions aremeasured. The amount of alkanolamine is adjusted to maximize the C_(p)in a particular formulation. Preferred compositions provide a C_(p)value under the desired development conditions of at least about 1.33when one micron lines are developed.

If the amount of alkanolamine is expressed as an amount sufficient toincrease the process latitude of the composition, process latitudevalues of the composition are measured. The amount of alkanolamine isadjusted to maximize the process latitude in a particular formulation.Preferred compositions provide a process latitude of at least about 1.33under the development conditions specified in the Examples.

In the method inventions defined herein, the primary novel element isselection of a developer composition according to the previously statedcomposition invention. It is not evident from any prior art known to theinventors that selection of this developer will allow a photoresist tobe developed under high contrast conditions without forming irregulardeposits on the edges of unexposed portions of the photoresist,providing a C_(p) value and a process latitude for the developer of atleast about 1.33.

Various modes of development are contemplated within the scope of thepresent invention. In immersion development, the coated and exposedwafers, either alone or in a boat of wafers, are supported in a bath ofthe selected developer for a sufficient time to develop thephotoresists. In spray process development individual wafers coated withthe photoresist are transported to a development site and developed byone or a sequence of operations including streaming the developer ontothe surface of the photoresist; spinning the wafer to remove excessmaterial, particularly fluid, from its surface; spraying the developerover a wide surface of the wafer; and puddling, which is done byallowing residual developer to remain as a meniscus or puddle coveringthe surface of the stationary wafer. Automated spray developmentequipment can be programmed to provide the desired sequence ofdevelopment steps, and to develop each wafer in a batch according to thedesired program.

EXAMPLE

The following examples are provided to illustrate practice of thepresent invention, including the best mode. The claims, and not theexamples, define the scope of the present invention.

Photoresist samples were prepared as follows. The substrate was asilicon wafer with a polyoxide surface coating, pre-treated withhexamethyldisilane to promote adhesion. EPR-5000, a novolak resin-basedcomposition sold by the Dynachem division of Morton Thiokol, Inc.,Tustin, California, was coated onto the substrate using conventionalautomated spin-coating equipment. The coating thickness was about 13,000Angstroms (1.3 microns), plus or minus about 300 Angstroms, and wasmeasured for each wafer individually. The coatings were dried andconditioned in the usual manner, providing sensitized substrates typicalof those used in the industry.

For all experiments, the sensitized substrates were exposed through anexposure mask on a step-and-repeat exposure tool with ultravioletradiation provided by a high pressure mercury vapor lamp. The size ofthe exposed image (24 millimeters by 14 millimeters) allowed severalexposures (18 or less) to be distributed on the surface of the substratewithout overlapping. It was possible either to incrementally increaseexposure energies at each exposure, or to repeat one exposure energyseveral times across the surface of the substrate.

Developer solutions were prepared by mixing the ingredients recitedbelow to provide one-gallon batches.

In the immersion testing, an entire batch of each developer solution waspoured into a large dish, forming a bath deep enough to completelyimmerse a wafer being developed. The exposed substrates were developedby manually immersing each one in the dish of developer. The immersiontime was one minute (60 seconds). Then, the substrates were removed fromthe dish of developer and rinsed by placing them in a cascade tank fedfrom the bottom with deionized water.

For spray/puddle development testing the development and rinsing stepswere performed using conventional automated spray development equipmentsold by Silicon Valley Group, San Jose, California. In each programseveral sequential steps were completed. For each step, the wafer wasrotated at the indicated rate while the indicated material was appliedin the indicated manner for the indicated amount of time, according toone of the schedules in Table II.

Film speed of the developer was evaluated by observing through anoptical microscope at 400× magnification the radiation dose necessary toresolve one micron lines of resist.

Linewidth uniformity (Critical Dimension Uniformity) is evaluated usingseveral exposures at the same dose across the surface of the substrate.Linewidth measurements are made at each of these exposures, themeasurements are averaged, and the standard deviation is calculated. Avalue called "C_(p) ", can be calculated from this data according to thefollowing formula:

    C.sub.p =delta L/6 sigma

Delta L is the difference between the minimum and maximum acceptablelinewidths of a line defined in the photoresist by a 1 micron line onthe exposure mask. Sigma is one standard deviation.

For a 1 micron nominal linewidth, the acceptable range of linewidths isdefined to be from 0.9 to 1.1 microns; delta L is thus (1.1-0.9)microns, or 0.2 microns. An acceptable value of sigma is defined hereinto be less than or equal to 0.025 microns. Presenting the sameinformation in terms of the C_(p), an acceptable value for C_(p) isdefined herein to be less than or equal to 1.33 microns.

Process latitude is a measure of a developer's ability to functionsatisfactorily despite defined variations in process parameters. Forpresent purposes process latitude is satisfactory if, at exposureenergies of from 220 to 260 mJ/cm² ; a resist thickness of 1.3 microns(plus or minus 0.1 microns) of EPR-5000 resist; a (resist) soft baketemperature of from 115° C. to 120° C.; a developer temperature of 15°C. (plus or minus 1° C.), or alternately a developer temperature of 18°C. (plus or minus 1° C.); and an exposure tool focus on the top of theresist (plus or minus 1.0 microns); C_(p) exceeds 1.33 microns. Processlatitude can be reported quantitatively as the minimum value of C_(p)over the defined range of exposure energies. The developers according tothe present invention have better process latitude than conventionalresists which do not contain alkanolamines.

In Examples 1-4, monoethanolamine, abbreviated "MEA", was used as analkanolamine according to the present invention. The proportions ofingredients and other information are set out in Table III. In theTables, development mode "I" indicates immersion development. "Spray 1"indicates spray development according to Program 1 set forth in TableII. The abbreviation "mJ/cm² " indicates the radiation exposure inmillijoules per square centimeter. "Result" provides a qualitativeindication of the result of the experiment. LR indicates low resolutionor a lack of resolution, meaning that the developer did not selectivelyremove the exposed portions of the photoresist while refraining fromattacking the unexposed portions thereof. "Poor spray" means that thecomposition was not properly atomized by the spray nozzle. "Poordevelop" means that exposed portions of the photoresist were not removedor were removed inadequately. The "ratio" is a recapitulation of theratio of TMAH to the alkanolamine, here MEA, providing a readycomparison of the development result with the ratio of theseingredients.

Looking at Table III, it will be evident that examples 1 and 2 providegood development in an immersion mode, while in Example 3 the spraypattern provided during spray development was considered poor,indicating that the material was developed but that irregulardevelopment is potentially present. Eample 4, in which only 0.5% TMAHand 80.0% MEA is employed as a developer, demonstrates that this is toolittle TMAH to provide proper development, even in the presence of 80%monoethanolamine. Example 4 also establishes that monoethanolamine byitself, even at high concentrations, is not a suitable developer for thepresent photoresist.

Table IV, in which the alkanolamine is 1-amino-2-hydroxypropane (species2 of Table I, identified in Table IV as 1,2-MPA), shows the results ofExamples 5-8. In this Table and subsequent Tables, "X-100" indicatesTRITON X-100 nonionic surfactant, identified previously in thespecification. "Spray 2" in the development mode line indicates SprayDevelop Program 2 in Table II. In the result column, "res." indicatesthat a residue was present on the edges of developed lines of thephotoresist.

1-amino-2-hydroxypropane sometimes provides a residue (Examples 5 and 8)and sometimes does not (Examples 6 and 7). It is better in an immersiondeveloper than in a spray developer; a poor spray pattern was notedduring spray development. The best result is obtained at a ratio of 1:18as in Example 7, in which no residue was noted on the developed lines.

Examples 9-18 in Tables V and VI show development with1-amino-3-hydroxypropane, abbreviated in Tables V and VI as 1,3-MPA.This is species 10 of Table I. Looking first at Table V, Examples 9 and10 are essentially identical runs, but in Example 9 a residue was notedat a ratio of 1:12, while in Example 10 no residue was noted. Thisindicates that this is a marginally acceptable formulation. Similarly,Examples 11 and 12 are essentially identical runs. In one case a residuewas provided, and in the other case no residue was observed. Examples9-12 were all run at a ratio of 1:12, which therefore is less preferredthan the 1:15 ratio of Example 13. A 1:15 ratio has been found in thisand other examples to almost never leave residue on the edges of thedeveloped resist lines. Thus, a ratio of 1:15 is preferred to provideoptimal development with minimal amounts of the alkanolamine.

Examples 14-18 show ratios of TMAH to 1,3-MPA of 1 to 15 or lower.Examples 14-16, using spray development, illustrate that the 1:15composition of 1,3-MPA can be sprayed successfully and provides residuefree development. The compositions of Examples 14-16 all contain TRITONX-100 surfactant, in increasing amounts. In Example 16 0.05% of thissurfactant was too much, as it caused developed resist line sidewalls toslope or otherwise deviate from the optimal vertical sidewalls. Thus,0.05% of this surfactant is more than the preferred maximum amount underthe other conditions of this example. Example 17 showed a ratio of 1:20and good development despite the presence of less TMAH than in the otherformulations. Example 18 illustrates that at extremely low ratios, evenwhen the amount of TMAH is minimized, the developed resist has a roughsurface. Roughness is believed to be caused by the presence of a largeamount of the alkanolamine. While some roughness can be tolerated, it isnot desirable, so a minimum ratio of about 1 to 38 is preferred herein.

Tables VII, VIII, and IX embody the results of comparative Examples19-34, using various similar compounds in place of the alkanolamines ofthe present invention.

In Table VII, Examples 19-23, the alkanolamine was replaced withethylene diamine (abbreviated EDA in the table) in ratios of from amaximum of 1:3 to a minimum of 1:37.8. In all cases immersiondevelopment was used. The relatively large proportion of TMAH in thehigh ratio of Example 19 stripped both developed and undevelopedportions of the resist from the substrate. The remaining examples allshow the formation of residue or heavy residue, and the lowest ratio ofTMAH (and highest ratio of EDA) provides a heavy residue and lack ofresolution which do not constitute suitable development. The inventorsconclude from this example that a wide range of different proportionsand ratios of ethylene diamine does not exhibit the beneficialproperties of the present invention.

Table VIII provides comparative examples 24-27 in which the alkanolamineis replaced with ethylene glycol (EG). Over a wide range of ratios andproportions of ethylene glycol, the result is again a residue on thedeveloped lines of photoresist, in either the immersion or the spraymode of development. Example 28 is prior art, and illustrates that aformulation containing just TMAH in a proportion sufficient to developthe photoresist provides a residue, and thus is not an optimal developeraccording to the present invention. As noted previously, Example 4 showsthe contrary situation in which a large amount of an alkanolamineaccording to the present invention is present (80%) and an insufficientproportion of TMAH is present. Comparing these examples, it is evidentthat neither TMAH alone nor an alkanolamine alone provides properdevelopment, but the other examples show that the combination of thesetwo ingredients improves development unexpectedly.

In Table IX, Examples 29 and 30 show the use of diethanolamine(abbreviated: DEA); comparative Examples 31 and 32 show the use oftriethanolamine (abbreviated: TEA); and comparative examples 33 and 34employ diethylethanolamine (abbreviated: DEEA) in place of the presentalkanolamines. In all these comparative examples, each in two differentproportions employing the immersion development mode, development washindered by the additive. In Examples 29-32, despite a high maximumexposure, only a latent image was produced. This means that the exposedportions of the photoresist were not removed by this formulation. InExamples 33 and 34 the developed and undeveloped portions of thephotoresist were both stripped.

The comparative examples illustrate that the class of additives whichprevent residue formation without disturbing the function of the resistdeveloper is narrow. Ethylene diamine differs from the presently claimedmonoethanolamine by substitution of a second amine for a hydroxy group.Ethylene glycol of comparative Examples 24-28 is different frommonoethanolamine only by the substitution of a second hydroxyl group forthe amine group. In short, a structure with an amine group on one endand a hydroxyl group on the other works, but respective structures withtwo amine groups or two hydroxyl groups in the same positions do notwork. The additives of comparative examples 29-34 differ from thepresent invention, and specifically from monoethanolamine, by thesubstitution of alkyl or ethanol moieties for the amine hydrogen atomsof the present generic formula. Diethanolamine has two ethanol moietiesinstead of the single ethanol moiety of monoethanolamine according tothe present invention. Triethanolamine has three ethanol moieties inplace of the single ethanol moiety of the present invention.Diethylethanolamine has two ethyl groups in place of the amine hydrogensof monoethanolamine. These substitutions all provide a compound whichdoes not function in the advantageous manner of the present alkanolamines.

The formulations and data for Examples 35-40 are reported in Table X.Exemplary two micron lines of each developed resist were photographedwith a scanning electron microscope at a magnification of 20,000diameters and an energy of 23 KV. FIGS. 1 through 6 respectivelycorrespond to Examples 35 through 40.

In FIG. 1 and Example 35, the developer was 1-amino-2-hydroxypropane ata ratio of 1:12. FIG. 1 illustrates some residue, particularly along theupper edges of the resist, but no roughness. (The slight roughness orgrain shown in the photographs on the top surface of each resist lineand on the substrate between the resist lines is a combination of noisein the microscope and photographic grain.) FIG. 1 shows a reduction ofthe residue problem, but not a complete solution.

In FIG. 2 and Example 36, the formulation contained1-amino-3-hydroxypropane at a ratio of 112. The result shown in FIG. 2is similar to that shown in FIG. 1.

In FIG. 3 and Example 37, a 1:15 ratio of 1-amino-3-hydroxypropane wasused; the formulation contained 1.00% of TMAH, and is consideredoptimal. As FIG. 3 shows, the developed lines have smooth upper surfacesand no visible residue. (The regular, horizontal striations on thesidewalls of the lines are artifacts of standing waves in the exposureradiation, and are not residue.)

In Example 38 and FIG. 4, the ratio of TMAH to 1-amino-3-hydroxypropaneis 1:37.9. The line is clearly developed and has no residue, but theentire top and side surfaces of the line are roughened; this isconsidered less than optimal development, although the advantages of thepresent invention other than absence of roughness are obtained in thisexample.

In Example 39 and FIG. 5, ethylene diamine is added to the developer ata ratio of 1:20. Heavy residue is present on the edges of the topsurface. The vertically oriented ridge-and-valley irregularity of thesidewalls is also related to the presence of the residue problem:

Example 40 and FIG. 6 illustrate development with a prior artformulation of 2.0% by weight TMAH and no other additives. FIG. 6 thusillustrates that without an alkanolamine a heavy residue is observed.

                  TABLE II                                                        ______________________________________                                        Spray Development Programs                                                           Wafer       Material         Duration                                  Step   Rotation    Applied    Mode  of Step                                   ______________________________________                                        Spray Develop Program 1                                                       1      50      rpm     Developer                                                                              Spray 42   sec.                               2      1,000   rpm     DI water Stream                                                                              10   sec.                               3      4,000   rpm     None     Dry   10   sec.                               Spray Develop Program 2                                                       1      1,000   rpm     DI water stream                                                                              2    sec.                               2      1,000   rpm     Developer                                                                              spray 10   sec.                               3      400     rpm     Developer                                                                              spray 5    sec.                               4      0       rpm     Developer                                                                              spray 2    sec.                               5      0       rpm     None     puddle                                                                              15   sec.                               6      1,000   rpm     DI water stream                                                                              10   sec.                               7      4,000   rpm     None     dry   10   sec.                               Spray Develop Program 3                                                       1      450     rpm     Developer                                                                              spray 7    sec.                               2      50      rpm     Developer                                                                              spray 4    sec.                               3      0       rpm     None     puddle                                                                              15   sec.                               4      50      rpm     Developer                                                                              spray 4    sec.                               5      0       rpm     None     puddle                                                                              15   sec.                               6      50      rpm     Developer                                                                              spray 4    sec.                               7      0       rpm     None     puddle                                                                              15   sec.                               8      1,000   rpm     DI water stream                                                                              10   sec.                               9      5,000   rpm     None     dry   10   sec.                               ______________________________________                                    

                  TABLE III                                                       ______________________________________                                        MEA, Examples 1-4                                                             Component  1        2         3      4                                        ______________________________________                                        Wt. % TMAH  1.60     1.00      1.00   0.50                                    Wt. % MEA   12.5     37.9      37.9   80.0                                    Wt. % H.sub.2 O                                                                           85.9     61.1      61.1   19.50                                   Total %    100.00   100.00    100.00 100.00                                   Development                                                                              I        I         spray  I                                        Mode                                                                          mJ/cm.sup.2                                                                              70       50        50     100                                      Result     good     good      poor   LR;                                                                    spray  poor                                                                          develop                                  Ratio      1:7.8    1:37.9    1:37.9 1:160                                    ______________________________________                                    

                  TABLE IV                                                        ______________________________________                                        1,2-MPA, Examples 5- 8                                                                  5      6         7        8                                         ______________________________________                                        Wt. % TMAH   1.25     1.25      1.00   1.05                                   Wt. % 1,2-MPA                                                                              15.0     15.0      18.0   21.0                                   Wt. % X-100                            0.01                                   Wt. % H.sub.2 O                                                                            83.75    83.75     81.00  77.94                                  Total %     100.00   100.00    100.00 100.00                                  Development I        spray 2   I      spray 2                                 Mode                                                                          mj/cm.sup.2 60       70        50     70                                      Result      res.     poor      good   res.                                                         spray            and                                                                           poor                                                                          spray                                   Ratio       1:12     1:12      1:18   1:20                                    ______________________________________                                    

                  TABLE V                                                         ______________________________________                                        1,3 MPA, Examples 9- 13                                                               9      10      11       12    13                                      ______________________________________                                        Wt % TMAH  1.20     1.20    1.20   1.20  0.96                                 Wt % 1,3MPA                                                                              14.4     14.4    14.40  14.40                                                                               14.40                                Wt % X-100                                                                              --       --        .01    .01   .01                                 Wt %H.sub.2 O                                                                            84.40    84.40   84.39  84.39                                                                               84.63                                Total %   100 00   100.00  100.00 100.00                                                                              100.00                                Develop-  spray    spray   spray  spray spray                                 ment Mode 2        2       2      2     1                                     mJ/cm.sup.2                                                                             60       60      80     70    190                                   Result    res.     good    res.   good  good                                  Ratio     1:12     1:12    1:12   1:12  1:15                                  ______________________________________                                    

                  TABLE VI                                                        ______________________________________                                        1,3 MPA, Examples 14- 18                                                              14     15      16       17    18                                      ______________________________________                                        Wt % TMAH  1.00     1.10    1.10   0.95  0.70                                 Wt % 1,3MPA                                                                              15.0     16.5    16.5   19.0  26.53                                Wt % X-100                                                                                .005     .01     .05  --    --                                    Wt % H.sub.2 O                                                                           83.995   82.39   82.35  80.05                                                                               72.77                                Total %   100.000  100.00  100.00 100.00                                                                              100.00                                Develop-  spray    spray   spray  I     I                                     ment Mode 1        1       1                                                  mJ/cm.sup.2                                                                             110      60      70     50    50                                    Result    good     good    side-  good  rough                                                            wall                                                                          slope                                              Ratio     1:15     1:15    1:15   1:20  1:37.9                                ______________________________________                                    

                  TABLE VII                                                       ______________________________________                                        Comparative Examples 19- 23                                                   Component 19       20      21     22    23                                    ______________________________________                                        Wt % TMAH  3.0      1.65    1.05   0.84  0.90                                 Wt % EDA   9.0      4.95    12.6   17.4  34.02                                Wt % H.sub.2 O                                                                           88.0     93.40   86.35  81.76                                                                               65.08                                Total %   100.0    100.00  100.00 100.00                                                                              100.00                                Development                                                                             I        I       I      I     I                                     Mode                                                                          mJ/cm.sup.2                                                                             10-100   50      50     50    60                                    Result    strip    res.    res.   res.  heavy                                                                         res.;                                                                         LR                                    Ratio     1:3      1:3     1:12   1:20  1:37.8                                ______________________________________                                    

                  TABLE VIII                                                      ______________________________________                                        Comparative Examples 24- 28                                                   Component 24       25      26     27    28                                    ______________________________________                                        Wt % TMAH  2.40     2.55    0.87   0.90  2.2                                  Wt % EG    7.20     30.6    17.40  34.02                                                                              --                                    Wt % H.sub.2 O                                                                           90.40    66.95   81.73  65.08                                                                               97.8                                 Total %   100.00   100.00  100.00 100.00                                                                              100.0                                 Development                                                                             I        I       spray  spray I                                     Mode                       2      2                                           mJ/cm.sup.2                                                                             60       80      70     50    50                                    Result    res.     res.    res.   heavy res.                                                                    res.                                        Ratio     1:3      1:12    1:20   1:37.8                                                                              --                                    ______________________________________                                    

                  TABLE IX                                                        ______________________________________                                        Comparative Examples 29- 34                                                   Component                                                                              29      30      31    32    33    34                                 ______________________________________                                        Wt &      1.00    1.00    1.00  1.00  1.00  1.00                              TMAH                                                                          Wt % DEA  10.00   20.00  --    --    --    --                                 Wt % TEA --      --       10.00                                                                               20.00                                                                              --    --                                 Wt % DEEA                                                                              --      --      --    --     10.00                                                                               20.00                             Wt % H.sub.2 O                                                                          89.00   79.00   89.00                                                                               79.00                                                                               89.00                                                                               79.00                             Total %  100.00  100.00  100.00                                                                              100.00                                                                              100.00                                                                              100.00                             Development                                                                            I       I       I     I     I     I                                  Mode                                                                          mJ/cm.sup.2                                                                            400     400     400   400   --    --                                 Result   latent  latent  latent                                                                              latent                                                                              strip strip                                       image   image   image image                                                   only    only    only  only                                           Ratio    1:10    1:20    1:10  1:20  1:10  1:20                               ______________________________________                                    

                  TABLE X                                                         ______________________________________                                        Component                                                                              35      36      37    38    39    40                                 ______________________________________                                        TMAH      1.25    1.20    1.00  0.70  0.84  2.0                               1,2-MPA   15     --      --    --    --    --                                 1,3-MPA   0       14.40   15.0  26.53                                                                              --    --                                 EDA       0      --      --    --     16.8 --                                 X-100     0      .01       .01 --    --    --                                 H.sub.2 O                                                                               83.75   84.39   83.99                                                                               72.77                                                                               82.36                                                                               98.00                             Total %  100.00  100.00  100.00                                                                              100.00                                                                              100.00                                                                              100.00                             Development                                                                            spray   spray   spray spray I     spray                              Mode     2       1       2     3           2                                  mJ/cm.sup.2                                                                            70      60      110   50    50    90                                 Result   res.    slight  good  rough heavy heavy                                       poor    res.                res.  res.                                        spray                                                                Ratio    1:12    1:12    1:15  1:37.9                                                                              1:20  --                                 ______________________________________                                    

We claim:
 1. A method for developing an image-wise exposed quinonediazide positive-working photoresist without forming irregular depositson the edges of unexposed portions of said photoresist, comprising thesteps of:A. providing said exposed photoresist; B. providing a developercomposition consisting essentially of an aqueous solution of atetraalkylammonium hydroxide present in an amount effective to enablesaid composition to develop said photoresist; and an alkanolamine havingthe following structure: ##STR3## wherein n is zero or one, each R isindependently selected from hydrogen, methyl, or ethyl, and the weightratio of said primary alkali to said alkanolamine is less than about1:9; C. developing said photoresist with said developer until theexposed portions of said photoresist are cleared; and D. rinsing saiddeveloper from said photoresist.
 2. The method of claim 1, wherein saidstep C is immersion development.
 3. The method of claim 1, wherein saidstep C is spray development.
 4. The method of claim 1, wherein saidalkanolamine is 1-amino-3-hydroxypropane.
 5. A method for developing animage-wise exposed quinone diazide positive-working photoresist in amanner providing a C_(p) value of at least about 1.33, comprising thesteps of:A. providing said exposed photoresist; B. providing a developercomposition consisting essentially of an aqueous solution of atetraalkylammonium hydroxide present in an amount effective to enablesaid composition to develop said photoresist; and an alkanolamine havingthe following structure: ##STR4## wherein n is zero or one, each R isindependently selected from hydrogen, methyl, or ethyl, and the weightratio of said primary alkali to said alkanolamine is less than about1:9; C. developing said photoresist with said developer until theexposed portions of said photoresist are cleared; and D. rinsing saiddeveloper from said photoresist.
 6. The method of claim 5, wherein saidC_(p) value is at least about 1.33 when said exposed photoresistthickness is 1.3 microns plus or minus 0.1 microns; the exposure energyused to expose said photoresist is from 220 to 260 millijoules persquare centimeter; the soft bake temperature for said photoresist isfrom 115° C. to 120° C.; the temperature of said developer is 15° C.,plus or minus 1° C.; and the tool used to expose said photoresist isfocused on the upper surface of said photoresist, plus or minus 1micron.